I think it is the latter, as I can't see the individual pieces of wood!
then I think it would not readily rack back to shape. You can actually pull old panelled doors back to shape easier than you'd think.
It might probably bend back, eventually, if you used, say, a bolt and a block of wood, but it might be very slow and awkward.
But I wonder why it has warped?
I have seen a chipboard door warp when it was damp on one side and dry on the other, and the damp side expanded so it curved. Does anything like that happen? is it painted, both sides and all four edges? Is it prone to condensation on the house side? Or is there water dripping on it?